The present invention relates generally to operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a sealed wellbore junction utilizing novel apparatus and methods.
Although it is common practice to drill one or more lateral wellbores extending outwardly from a parent wellbore, sealing junctions between the parent wellbore and the lateral wellbores has presented difficult problems for designers of drilling and completion systems. One of the basic problems has been to provide fluid communication with, and access to, each of the wellbores while isolating the earthen formation surrounding the junction from fluids produced from, or injected into, the wellbores.
Various solutions to this problem have been proposed, many of which involve using cement to isolate the junction from fluid flow through the wellbores. However, it would be advantageous to instead use a more ductile and accurately dimensioned material, such as metal, to construct a pressure-bearing conduit for fluid flow through the junction between the wellbores. Unfortunately, the constraints of working within the confines of a well, and the need for passing equipment having specified diameters through flow passages of the junction, have heretofore resisted attempts at a convenient and economical solution to this problem.
For example, it may be dimensionally impossible in certain situations to convey flow passages for a lateral wellbore and for a lower portion of the parent wellbore side-by-side into the well. This is especially so where the diameter of the parent wellbore above the junction is less than the combined diameters of the lower parent wellbore and lateral wellbore flow passages. Therefore, it may be necessary or desirable to separately convey these flow passages into the well.
However, if the flow passages are separately conveyed into the well, they must be joined together later within the well. This presents the problem of arranging and sealingly engaging the members in which the flow passages are formed within the confines of the well.
From the foregoing, it can be seen that it would be quite desirable to provide a method of sealing a wellbore junction which does not rely solely upon cement for sealing the junction, but which conveniently and economically results in a sealed junction having relatively large diameter flow passages for each wellbore. It is accordingly an object of the present invention to provide such a method and associated apparatus.